Improvement and Application of the Similarity Saltation Model: Wind-Tunnel Experimental Investigation and Numerical Simulation of the Vertical Sand Mass Flux Distribution in the Saltation Layer

Based upon comparisons between published experimental data and simulated results on the vertical sand flux distribution in the saltation layer, Shao’s similarity saltation model has been greatly improved by correcting the average vertical particle lift-off velocity and using a more suitable universal roughness length. By the improved model, the vertical sand flux profile over the bare, dry and loose uniform sandy surface, which is quite representative of real desert surfaces, can be reproduced very well. Meanwhile, the surface transport rate and the characteristic and average saltation heights have been simulated and analyzed in detail, disclosing their relationships with friction velocity, particle size and roughness length, and the possible underlying mechanisms. Besides, the average particle lift-off velocity and the average mean vertical aerodynamic action upon the ascending particle, which determine the saltation process, are explicitly expressed by parameters involved in the similarity model, and their relationships with friction velocity, particle size and roughness length are also described concisely. The corrected average particle lift-off velocity makes it possible to investigate the characteristic particle trajectory, whose initial velocity equals the average lift-off velocity, so as to estimate the average particle against surface impacting velocity and the average aerodynamic action upon the saltation process.     

近48a台北市气温的小波分析

利用Morlet小波分析了1961—2008年台北市年平均气温序列的小波变化特征,揭示了气温变化的多时间尺度结构,结果表明:台北市年平均气温存在多时间尺度的周期变化特征,有3个明显的特征时间尺度,分别是4 a、6-8 a和14-16 a;除14-16 a的时间尺度在整个研究时段都很明显外,其他尺度的周期阶段性都较强;以14-16 a的特征时间尺度为主周期;台北市的气温变化还表现出突变的特点;近48 a来,台北市年平均气温的气候倾向率为0.3℃/10 a,气温升高的趋势十分明显;未来2年气温在总趋势上升的前提下将处在一个偏冷期。     

Parameterization of Sheared Convective Entrainment in the First-Order Jump Model: Evaluation Through Large-Eddy Simulation

In this note, two different approaches are used to estimate the entrainment-flux to surface-flux ratio for a sheared convective boundary layer (CBL); both are derived under the framework of the first-order jump model (FOM). That suggested by Sun and Wang (SW approach) has the advantage that there is no empirical constant included, though the dynamics are described in an implicit manner. The second, which was proposed by Kim et al. and Pino et al. (KP approach), explicitly characterizes the dynamics of the sheared entrainment, but uncertainties are induced through the empirical constants. Their performances in parameterizing the CBL growth rate are compared and discussed, and a new value of the parameter A ₃ in the KP approach is suggested. Large-eddy simulation (LES) data are employed to test both approaches: simulations are conducted for the CBL growing under varying conditions of surface roughness, free-atmospheric stratification, and wind shear, and data used when the turbulence is in steady state. The predicted entrainment rates in each case are tested against the LES data. The results show that the SW approach describes the evolution of the sheared CBL quite well, and the KP approach also reproduces the growth of the CBL reasonably, so long as the value of A ₃ is modified to 0.6.     

玉米螟越冬死亡率的气象条件及其预报模型研究

根据1994-2004年黑山气象资料和玉米螟越冬期资料,采用通径分析方法,对玉米螟越冬期的气象条件与死亡率的关系进行分析,建立了4月和5月死亡率的预报模型。结果表明：玉米螟受3-5月的气象因子影响较大,死亡率明显高于越冬前的死亡率,建立的模型能够反映玉米螟越冬期气象条件与死亡率的响应关系,可在实际预报业务中作为参考依据。考虑越冬前死亡率的预报拟合率明显高于不考虑越冬前死亡率的模拟结果,说明在对玉米螟进行预报时,只考虑气象因子,不考虑虫源基数是不全面的。     

Study of the dependence of the star formation rate in the nuclear regions of 39 Kazarian galaxies on their integral parameters

A statistical study of the dependence of the star formation rate in the nuclear regions of 39 Kazarian galaxies on the integral parameters of these galaxies is carried out on the basis of spectra from SDSS DR6. The value of SFR/kpc² for our sample lies in the range 0.013÷2.04M _⨀ year⁻¹kpc⁻² (with the maximum value of 2.04 corresponding to the Kaz 98 (merger)). It is found that the surface density of the rate of star formation correlates positively with the bar structure parameter and EW(Hα), and that, for spiral galaxies of early morphological types, SFR/kpc² is greater than for the later types. It is shown that the color B-R for the galaxies and the color (u − g) _nucl for the nuclear region correlate positively with the total absorption A(Hα) in the Ha line for the nuclear region. The average value of A(Hα) for our samples is found to be A(Hα)=1.3±0.09 magnitudes. Translated from Astrofizika, Vol. 52, No. 2, pp. 211–224 (May 2009).     

无线传感器网络中基于时钟漂移补偿的时间同步技术

在分析和总结现有时间同步算法的特点及其存在问题的基础上,提出了一种在无线传感器网络的时间同步协议（TPSN）中同时考虑节点时钟偏移和频率漂移率的改进算法。该算法利用连续两次同步过程中所记录的时间信息来估算节点时钟的偏移和频率漂移率,并进行补偿。同传统算法相比,此算法通讯成本较低、精度较高。最后通过数学分析和仿真的方法对所提出的改进算法进行了验证。     

On the swelling potential of compacted high plasticity clays

We conducted a study of the spatial distributions of seismicity and earthquake hazard parameters for Turkey and the adjacent areas, applying the maximum likelihood method. The procedure allows for the use of either historical or instrumental data, or even a combination of the two. By using this method, we can estimate the earthquake hazard parameters, which include the maximum regional magnitude Mˆ_max, the activity rate of seismic events and the well-known bˆ value, which is the slope of the frequency-magnitude Gutenberg-Richter relationship. These three parameters are determined simultaneously using an iterative scheme. The uncertainty in the determination of the magnitudes was also taken into consideration. The return periods (RP) of earthquakes with a magnitude M ≥ m are also evaluated. The whole examined area is divided into 24 seismic regions based on their seismotectonic regime. The homogeneity of the magnitudes is an essential factor in such studies. In order to achieve homogeneity of the magnitudes, formulas that convert any magnitude to an M_S-surface scale are developed. New completeness cutoffs and their corresponding time intervals are also assessed for each of the 24 seismic regions. Each of the obtained parameters is distributed into its respective seismic region, allowing for an analysis of the localized seismicity parameters and a representation of their regional variation on a map. The earthquake hazard level is also calculated as a function of the form Θ = (Mˆ_max,RP_6.0), and a relative hazard scale (defined as the index K) is defined for each seismic region. The investigated regions are then classified into five groups using these parameters. This classification is useful for theoretical and practical reasons and provides a picture of quantitative seismicity. An attempt is then made to relate these values to the local tectonics.     

Conflicting structural and geochronological data from the Ibituruna quartz-syenite (SE Brazil): Effect of protracted “hot” orogeny and slow cooling rate?

The Ibituruna quartz-syenite was emplaced as a sill in the Ribeira-Araçuaí Neoproterozoic belt (Southeastern Brazil) during the last stages of the Gondwana supercontinent amalgamation. We have measured the Anisotropy of Magnetic Susceptibility (AMS) in samples from the Ibituruna sill to unravel its magnetic fabric that is regarded as a proxy for its magmatic fabric. A large magnetic anisotropy, dominantly due to magnetite, and a consistent magnetic fabric have been determined over the entire Ibituruna massif. The magmatic foliation and lineation are strikingly parallel to the solid-state mylonitic foliation and lineation measured in the country-rock. Altogether, these observations suggest that the Ibituruna sill was emplaced during the high temperature (~ 750 °C) regional deformation and was deformed before full solidification coherently with its country-rock. Unexpectedly, geochronological data suggest a rather different conclusion. LA-ICP-MS and SHRIMP ages of zircons from the Ibituruna quartz-syenite are in the range 530–535 Ma and LA-ICP-MS ages of zircons and monazites from synkinematic leucocratic veins in the country-rocks suggest a crystallization at ~ 570–580 Ma, i.e., an HT deformation > 35My older than the emplacement of the Ibituruna quartz-syenite. Conclusions from the structural and the geochronological studies are therefore conflicting. A possible explanation arises from ⁴⁰Ar–³⁹Ar thermochronology. We have dated amphiboles from the quartz-syenite, and amphiboles and biotites from the country-rock. Together with the ages of monazites and zircons in the country-rock, ⁴⁰Ar–³⁹Ar mineral ages suggest a very low cooling rate: < 3 °C/My between 570 and ~ 500 Ma and ~ 5 °C/My between 500 and 460 Ma. Assuming a protracted regional deformation consistent over tens of My, under such stable thermal conditions the fabric and microstructure of deformed rocks may remain almost unchanged even if they underwent and recorded strain pulses separated by long periods of time. This may be a characteristic of slow cooling “hot orogens” that rocks deformed at significantly different periods during the orogeny, but under roughly unchanged temperature conditions, may display almost indiscernible microstructure and fabric.     

纳米铁去除饮用水中As(Ⅲ)和As(Ⅴ)

在好氧水体中,As(Ⅲ)比As(Ⅴ)更易迁移,而且在水处理过程中去除效率更低。在实验室合成制得BET比表面积为49.16 m2/g,直径范围为20~40 nm的纳米铁。通过批试验考察纳米铁对As(Ⅲ)和As(Ⅴ)去除能力及其反应动力学情况。结果表明,在pH为7,温度20℃时纳米铁能够快速地去除As(Ⅲ)和As(Ⅴ),在60 m in内,0.25 g纳米铁对起始浓度为968.6μg/L As(Ⅲ)和828.9μg/L As(Ⅴ)的去除率大于99.5%。反应遵循准一级反应动力学方程,标准化后的As(Ⅲ)和As(Ⅴ)比表面积速率常数kSA分别为1.30 mL/(m2.m in)和1.64 mL/(m2.m in)。由实验结果可知,具有高反应活性的纳米铁是用于含砷饮用水处理非常有效的吸附材料。     

安徽绩溪伏岭岩体隆升时代的磷灰石裂变径迹证据

安徽绩溪伏岭岩体位于安徽省南部、黄山花岗岩体的东部。伏岭岩体裂变径迹（AFT）热年代分布于51±5～68±7 Ma之间,围限径迹长度为11.9～12.9μm。岩体形成之后,所在山系经历了速率波动较大的隆升过程,至55 Ma期间为一加速隆升过程,到55 Ma时速度达到最大的73 mm/ka;随后速度减缓,54 Ma左右时的平均抬升速率为60 mm/ka;54～51 Ma间又是一个快速加速隆升时期,到51 Ma时,速度达到70 mm/ka。研究区具有三个主要的冷却剥露阶段：130～116 Ma左右,冷却速率约为1.34℃/Ma;70～60 Ma左右,进入第二个较为快速冷却阶段,冷却速率约为25℃/Ma;在7～8 Ma左右发生突然加剧冷却事件,持续至今,速率达到8℃/km。总体来说,伏岭岩体经历了速率逐渐增加的冷却过程。由于黄山山体与伏岭岩体在大地构造位置、岩性特征及侵入时间上具有很大的相似性,二者的隆升时代、速率以及抬升剥蚀量是大致相当的。